The present invention relates to a gas-liquid contacting method and apparatus, more particularly to a gas-liquid contacting method and apparatus for contacting a flue gas containing pollutants, such as sulfur dioxide, which is poisonous to men and beasts when discharged to the atmosphere, with an absorbent liquid of said pollurants.
Recently, the so-called wet-type desulfurization method has greatly developed, which is adapted for removing sulfur dioxide contained in a flue gas of boilers of power plants, sulfuric acid plants and so on in the wet method, but the basic type of this desulfurization method is such one, except for the waste gas desulfurization method in pulp factories, that SO.sub.2 in a waste gas is once fixed as sulfurous acid salt and thereafter is oxidized to sulfuric acid salt thereby fixing it in this form. This method may be roughly classified from the viewpoint of the SO.sub.2 absorption agent, namely SO.sub.2 fixing agent, into the caustic soda absorption method, the ammonia absorption method, the lime absorption method, the sulfuric acid absorption method and the magnesium oxide absorption method etc., and it has been the present situation that due to the difference of SO.sub.2 fixing agent a variety of kinds of by-product compounds, namely sulfuric acid salts are produced, with the result that according to the kind of the SO.sub.2 fixing agent, the devices per se become greatly varied and complicated.
Also, in the case that a great capacity of the waste gas, such as, for example, 100 million Nm.sup.3 /hr.-200 million Nm.sup.3 /hr. is treated, it is the present status that since a pressure drop necessary for the absorption can not be made large, the absorption apparatus becomes necessarily large.
Particularly, in the case that the contact of a large capacity of gas and liquid and the precipitation of solids are performed continuously, since respective devices have different functions and constructions, it has been the general manner to adopt such a system that a gas-liquid contacting device and a solid precipitation device are respectively mounted separately and these are connected through pipings by using a pump as driving source.
The inventors et al. of the present invention have studied about concentrating said gas-liquid contacting device and the solid precipitation device and uniting them in one body many-sidedly, and found that in the case that only the prior art systems are combined, the devices become complicated and large in size without obtaining advantages of the concentration of the devices and in view of this, such a problem can be solved by adopting a new gas-liquid contacting system which permits the existence of solids.
Namely, it has been found that in the wet-type waste gas desulfurization method, one of the systems for making the device most compact is a method of absorbing sulfur dioxide and performing oxidation by means of oxygen containing gas simultaneously and at the same position.
However, in order to realize this method effectively, it has been a problem how to allow oxygen which is slow in the absorption speed compared with sulfur dioxide to be absorbed in the absorbent liquid to the same extent as sulfur dioxide. Accordingly, the present inventors et al. have studied earnestly further about obtaining an industrial method and apparatus which is possible to perform the absorption and oxidation of pollutants such as sulfur dioxide efficiently and at a stroke and as a result the present invention has been attained.